1. Field of the Invention
This invention relates to concealed fastener roof or wall structures, and more particularly to an improved concealed fastening arrangement for conforming the width of each panel member with a selected modular width during installation of the panel members.
2. Description of the Prior Art
Roof and wall structures are known wherein plural panels are assembled in side-by-side overlapped relation and secured in place by concealed fastening means entirely from beneath the panels and without requiring holes of any kind in the panels. Such an arrangement provides a structure which is leakproof.
Recent innovations in concealed fastening arrangements provide roof or wall structures using relatively wide panel members, e.g., 36" wide. Such panel members have downwardly opening, lengthwise extending, intermediate ribs, and complimentary partial ribs along opposite longitudinal edges thereof. The partial ribs are interfittable with complimentary partial ribs of adjacent panels to form joint ribs duplicating the cross-sectional configuration of the intermediate ribs. A first of such innovations is disclosed in U.S. Pat. No. 4,285,182 (DINGES). DINGES discloses a panel construction for roofs or walls which utilizes locating strips applied along the structural elements for temporarily locating the clips at uniformly spaced positions corresponding with the spacing of the intermediate and joint ribs of subsequently applied panel members. The clips and locater strips are secured to the structural elements by positive fasteners. Thereafter, the panel ribs are forced onto the clips by pressure applied to the top surfaces of the panels. The locater strip is intended to preclude rib-to-clip and joint-to-clip misalignment. The DINGES arrangement performs satisfactorily only if the spacing of the complimentary partial ribs and the intermediate ribs corresponds substantially to the clip spacing defined by the locater strip.
A second of such innovations is disclosed in copending application Ser. No. 249,062 (BOYER) filed Mar. 30, 1981 and assigned to the assignee of this invention and now U.S. Pat. No. 4,400,922. BOYER discloses a two-piece clip assembly configured to accommodate thermal movement of the panel members, that is expansion and contraction due to temperature changes. The two-piece clip assemblies also are configured to accommodate any joint-to-clip and rib-to-clip misalignment. The clip assemblies include base members secured to the structural elements at uniformly spaced locations therealong; and floating top clips capable of limited movement relative to the base members in a direction transverse to the panel ribs. The floating top clips accommodate minor variations in rib spacing and possible misalignment of the clips with respect to the ribs with which they must engage. The floating top clips center themselves within the ribs thereby minimizing drag between the clip and the panel during thermal movement of the panel; and thereby maximizing the hold-down capacity of the clips under wind uplift conditions.
Panel members are fabricated by roll forming operations to established manufacturing tolerances to provide, for example, a 36" (91.44 cm) coverage width. However, the actual coverage width of the panel members may vary from the intended 36" coverage width, by as much as .+-.3/16" (.+-.0.476 cm). The variations in coverage width may be caused by variations in the thickness of the sheet metal and of the decorative coating which must be accommodated by the rolls of the roll forming equipment; and by coil-to-coil variations in the physical properties of the steel. These variations cause varying degrees of permanent set and spring back in the material being roll formed thereby causing variations in the final shape of the ribs and hence in the coverage width. Since the panel coverage cannot be precisely controlled at the time of manufacture, any roof or wall installation must be engineered assuming 36" coverage width. The panels must be installed to provide the 36" coverage width regardless of the actual manufactured panel width. This can be accomplished in profiled panels by "moduling" the panel member, that is by physically stretching or compressing the panel to conform its width to the engineered width.
It appears that the DINGES clip arrangement cannot accommodate panel width variation without introducing undesirable assymetrical stresses which would compromise the holddown capacity of the clip and which may cause jamming during thermal movement of the panel.
The BOYER arrangement is intended to accommodate minor panel width variations since the floating top clip is capable of movement transversely of the panel ribs. However, any rib-to-clip and joint-to-clip misalignment caused by clip spacing errors created during clip installation, combined with panel width variations may cause the top clips to be jammed to one side of the base members. The jamming may cause the clips to bind in the ribs during thermal movement of the panel, and may reduce the hold-down capacity of the clip assemblies. If all of the top clips must be moved in the same direction because of width variations in the previously installed panels, the remaining top clips may not be capable of accommodating variations in manufacturing tolerances and in panel widths.